Memory devices typically include memory elements for storing data. “Flash” electrically erasable and programmable read only memories (EEPROMs) can include an electrical storage gate layer for altering a transistor threshold voltage. Thus, such devices may sense data values based on a transistor threshold voltage.
Devices having one time programmable elements, such as “anti-fuse” elements, can program an element by creating a non-reversible conductive path. Thus, such devices may sense data values based on a static resistance of the cell.
Conventional conductive bridge random access memories (CBRAMs) may include memory elements (sometimes referred to as programmable metallization cells (PMCs)) that may be programmed (or erased) to different resistance levels. Many PMC cells may have a metal-insulator-metal (MIM) structure. In one state (e.g., erased), substantially no current may flow through the MIM structure. In another state (e.g., programmed), a conductive path may be formed through the insulator layer. Accordingly, such memory devices may sense data values based on a resistance of a storage element (e.g., PMC).
In all of these conventional examples, it is intended that the sense operation measure a property of the memory cell that remains substantially unchanged over the duration of the operation. Other operations, typically called “write” and “erase,” are employed to change the value of the property that is to be sensed. Likewise, it is intended that the property to be sensed also remain substantially unchanged in between operations. Changes that do occur may be considered “errors,” and additional “correction” operations may be employed to return the property of the cell to its intended value. In contrast, during a write or erase operation, the property to be sensed will change with time, and no data value may be assigned to the cell.